1. Field of the Invention
The present invention relates to a method of forming a metal line of a semiconductor device, and more specifically to a method of forming a metal line of a semiconductor device capable of minimizing damage on an underlying element due to plasma-induced charges accumulated in the metal line in an over-etching process during forming the metal line connected to the underlying element.
2. Discussion of Related Art
Generally, a metal line is connected to an underlying element by carrying out a main etching process and an over-etching process using a plasma etching method after depositing a metal layer. During the process of forming the metal line, charges induced by plasma are accumulated in the metal line, which serve as a charging antenna, whereby the charges accumulated in the metal line damage the underlying element.
FIGS. 1A to 1F are cross-sectional views illustrating a conventional method of forming a metal line of a semiconductor device.
Referring to FIG. 1A, an underlying element 11 is formed on a semiconductor substrate 10. The underlying element 11 includes all unit elements employed in the present invention.
Referring to FIG. 1B, an interlayer insulating film 12 is formed on the semiconductor substrate 10 including the underlying element 11. A metal line contact hole 13 is formed by etching a portion of the interlayer insulating film 12 to expose a portion of a top surface of the underlying element 11.
Referring to FIG. 1C, conductive materials fill an inner portion of the metal line contact hole 13, so that a metal line plug 14 is formed to be connected to the underlying element 11.
Referring to FIG. 1D, a metal layer 15 is formed on the interlayer insulating film 12 including the metal line plug 14. A photoresist pattern 16 is formed on the metal layer 15 to cover a portion, in which the metal line is formed, including a top surface of the metal line plug 14.
Referring to FIG. 1E, a main etching process is carried out using a plasma etching method to etch the exposed portion of the metal layer 15.
Referring to FIG. 1F, the metal line 150 connected to the metal plug 14 is formed by carrying out an over-etching process for eliminating the metal layer 15, which remains even after performing the main etching process.
In processes mentioned above, charges induced by plasma during the main etching process using the plasma etching method are accumulated in the metal layer 15. In the main etching process, the plasma-induced charges do not damage the underlying element because the metal layer 15 on a wafer is electrically connected, not isolated. However, since the metal line 150 formed by the over-etching process is completely isolated not electrically connected, the metal line 150 serves as a charging antenna, so that the charges accumulated in the metal line 150 during the main etching process and the over-etching process electrically damage the underlying element 11 to deteriorate reliability thereof. When a multi-layer metal line is formed, damage on the underlying element 11 due to the charges is significantly increased because the aforementioned plasma damage is repeatedly accumulated.
Damage on the underlying element 11 due to the plasma-induced charges is affected by a layout of an antenna structure of the metal line 150, which is disclosed in Journal of the Korean Physical Society, Vol. 35, December 1999, pp. S742 to S746, entitled “Effect of Plasma Induced Charging in Interconnect Metal Etch on the Characteristics of a Ferroelectric Capacitor”.